1. Field of the Invention
This invention relates to a method and device for treating ULSI semiconductors represented by Si wafer under high-temperature, high-pressure atmosphere and, particularly, to a method and device for treating semiconductor wafers in a small lot of 1 to 25 pieces.
This invention further relates to a device used for a treatment of removing pores mainly by the pressure of an inert gas, such as a so-called pressure filling method for wiring film (high-pressure reflow process) of pressure treating a wafer having a copper alloy wiring film formed thereon by PVD, electrodeposition, CVD or the like by the inert gas pressure, and a method for using it, wherein the heating is performed in a short time to reduce generation of particles causing the contamination of a semiconductor substrate.
2. Description of the Related Art
As the process of treating semiconductor wafers under a high-pressure gas atmosphere by use of a vertical boat (wafer stacking jig), high-pressure oxidation process of oxidizing the surface of a Si wafer to form an insulator layer thereon is known. As the vertical device for this process, a one disclosed in Japanese Patent Application Laid-Open No. 4-234119 is known.
Since this device is entirely different in use and pressure level from the high-temperature, high-pressure treatment method using a perfectly inert gas that is intended by this invention, but similar in structure, it is shown as an example of known devices for reference.
This device is "a treatment device for semiconductor wafer comprising a pressure vessel; a hollow body having a treatment chamber within the pressure vessel, each of the pressure vessel and the hollow body having a lower opening part for receiving wafers in the movement of a plurality of wafers as one unit from the position under the pressure vessel to the position within the treatment chamber; operating means vertically movable to the pressure vessel in order to block the opening part; means connected to the hollow body in order to introduce a high-pressure oxidizer into the treatment chamber; means for introducing a pressurized inert gas into the treatment chamber; means for heating the oxidizer in the treatment chamber; means for cooling the hollow body after the treatment of the wafers in the treatment chamber; and means connected to the pressure vessel and the hollow body to equalize the pressures of the inert gas and oxidizer and connected to a body to equalize the pressures of the inert gas and oxidizer to substantially isolate the inert gas from the oxidizer". The wafers as workpiece are treated in the state housed in a vertical boat loadable of tens to a hundred and tens of pieces.
The most different point of the heating treatment of the semiconductor substrate from the treatment of other materials and members is that adhesion of dust called particles cannot be permitted.
The second different point is that extremely high productivity, or a short-time treatment is required because of the treatment within a clean room having high construction and maintenance costs.
This point is taken into consideration in the prior art and, for example, the high-pressure oxidizing device shown in FIG. 12 of Japanese Patent Application Laid-Open No. 4-234119 adapts, in order to prevent the adhesion of particles to the wafers, the structure of arranging a main heater (heating means 114) and an upper heater 124 on the outside of a bell jar 95 for housing wafers, which consists of a thin-wall inert material, for example, quartz to shield the direct inflow of the particles generated in the main heater part to the wafer side.
In FIG. 12 of Japanese patent Application Laid-Open No. 4-234119, a flat heater 125 is arranged in the lower part of the treatment chamber space formed by the bell jar in the form seen as if it is exposed to the treatment chamber, while this heater is constituted so as not to be exposed to the treatment chamber by a bottom 15 according to FIG. 21 of the same. It is consequently apparent that the heater is constituted so as not to be directly exposed to the treatment chamber at all.
In this conventional example, it is one of characteristics that the heater is made of graphite, and no ceramics is used except quartz as the insulating material in order to prevent the contamination of the wafers with heavy metals. However, inclusion of moisture or oxygen in air is actually unavoidable even in the treatment under inert gas atmosphere intended by this invention, and the use of graphite as the material of the heater is the question because of the generation of carbon dioxide (CO.sub.2) or hydrocarbonaceous gas (C.sub.m H.sub.n) by the reaction of graphite with oxygen or water in electric heating and the resulting generation of sort (regarded as a kind of dust).
Another problem in such a prior art is that the rise of internal temperature of the bell jar is rather delayed to makes the precise program control of temperature to time, in contrast with the quick temperature rise of the heater part when a high-speed temperature rise is performed in temperature rising process, because the wafers as workpiece are surrounded by the bell jar and heated by the heater arranged on the outside thereof. In cooling process, also, the bell jar is the barrier to diffusion of heat to cause the problem of requiring much time for cooling.
In addition to the situation of the prior art as described above, the recent tendency of enlargement of the wafer or change in diameter from 8 in. to 12 in. is causing the possibility of changing the lot size of the semiconductor wafers to be managed in lot unit. In the present manufacturing process intended for 8-in. wafers, it is standard that 25 pieces are housed in one cassette, and in the above prior art, also, the quality management of product is performed with 25, 50 and 100 pieces, which are multiples of 25, as one lot.
When the wafer is enlarged to 12 in., it is estimated that this minimum unit is changed to a unit smaller than 25 pieces, for example, 13 pieces, and in logic semiconductors that cannot help depending on small lot multi-production, particularly, the possibility of the dominance of the production in a further smaller lot is suggested. Under such circumstances, in respect to the manufacturing device, also, a device flexibly operable according to volume with a lot as small as possible might come to the force as the form of the device in future with high probability.
Accordingly, even in the batch type device as shown as the prior art, a one treatable in a small lot is increasingly required. On the other hand, the oxidation treatment shown as one example of the prior art has many subjects such as necessity of a long time even in a small lot, because formation of the oxide film by oxidizing phenomenon depends on time.
Such a treatment with little limitation on treatment time can be constructed with a process of treating a small lot in a short time so as not to lose the productivity. It is known that such a limitation on time is lessened in the treatment with a high-temperature, high-pressure gas represented by the pressure filling of metal wiring film.
Accordingly, this treatment is conformable to a demand of treating such a small lot in a short time offsetting it. In this case, it is a great subject that what small lot can be treated with a device as small as possible. Namely, it is important that how the maximum number of wafers are treated with a device having a small treatment capacity.
In any case, it is difficult to suppress the generation of particles from the electric furnace part in a vertical furnace for performing the treatment in batch, including a one using a high-pressure gas shown in the prior art, and it is common practice to house the semiconductor wafers as workpiece in the bell jar consisting of an airtight material.
On the other hand, in this bell-jar structure, the delay of temperature rise in the processing chamber space on the inside of the bell jar to the supply of heat by the heater part arranged on the outside of the bell jar makes the precise control of temperature difficult and also leads to the increase in diameter of the heater, resulting in the enlargement of the whole device.